SOME EFFECTS OF ETHYLENE ON THE 

 METABOLISM OF PLANTS 



CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 207 



Edward Maris Harvey 



(with two figures) - • ■ 



Introduction 

 Etiolated pea seedlings develop abnormally when they are 

 grown in the "impure air" of a laboratory. This response to 

 atmospheric impurities has become well known through the 

 work of Neljubow (25) and others. Three phases, at least, 

 are usually distinguished in the response of the epicotyl of the 

 seedling: (1) a retardation in the rate of elongation, (2) swelling, 

 and (3) a change from negative geotropism to diageotropism. 

 Furthermore, this characteristic response can be produced by a large 

 number of chemical compounds. However, the three phases 

 mentioned are not induced with equal ease; the third may never 

 appear for a given substance, although that substance readily 

 causes swelling and interferes with the rate of elongation. ' Like- 

 wise, both the second and the third may not appear, although there 

 is a marked retardation of growth. The swelling of developing 

 plant organs in the presence of poisonous substances is a very com- 

 mon response, especially when the concentration of the substance 

 in question is near the lower toxic limit. So frequently does this 

 phenomenon occur that one is perhaps justified in saying that swel- 

 ling is one of the first superficial indices of a disturbance in the 

 metabolism of a plant. 



Of the large number of chemical compounds capable of inducing 

 swelling in the pea seedling, ethylene has been found to be the most 

 effective. According to Knight, Rose, and Crocker (19), 

 ethylene will cause swelling of the epicotyl of the sweet pea seedling 

 I in dilutions of about 0.00004 per cent (by volume), while to pro- 

 ! duce similar results with chloroform, for example, the concentration 

 ig3 [Botanical Gazette, vol. 60 



